[llvm] r313108 - [InstCombine] Add a flag to disable LowerDbgDeclare
Reid Kleckner via llvm-commits
llvm-commits at lists.llvm.org
Tue Sep 12 18:43:25 PDT 2017
Author: rnk
Date: Tue Sep 12 18:43:25 2017
New Revision: 313108
URL: http://llvm.org/viewvc/llvm-project?rev=313108&view=rev
Log:
[InstCombine] Add a flag to disable LowerDbgDeclare
Summary:
This should improve optimized debug info for address-taken variables at
the cost of inaccurate debug info in some situations.
We patched this into clang and deployed this change to Chromium
developers, and this significantly improved debuggability of optimized
code. The long-term solution to PR34136 seems more and more like it's
going to take a while, so I would like to commit this change under a
flag so that it can be used as a stop-gap measure.
This flag should really help so for C++ aggregates like std::string and
std::vector, which are typically address-taken, even after inlining, and
cannot be SROA-ed.
Reviewers: aprantl, dblaikie, probinson, dberlin
Subscribers: hiraditya, llvm-commits
Differential Revision: https://reviews.llvm.org/D36596
Modified:
llvm/trunk/lib/Transforms/InstCombine/InstructionCombining.cpp
llvm/trunk/test/Transforms/InstCombine/debuginfo-skip.ll
llvm/trunk/test/Transforms/InstCombine/debuginfo.ll
llvm/trunk/test/Transforms/Util/simplify-dbg-declare-load.ll
Modified: llvm/trunk/lib/Transforms/InstCombine/InstructionCombining.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstructionCombining.cpp?rev=313108&r1=313107&r2=313108&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstructionCombining.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstructionCombining.cpp Tue Sep 12 18:43:25 2017
@@ -52,6 +52,7 @@
#include "llvm/Analysis/TargetLibraryInfo.h"
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/IR/CFG.h"
+#include "llvm/IR/DIBuilder.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/Dominators.h"
#include "llvm/IR/GetElementPtrTypeIterator.h"
@@ -91,6 +92,16 @@ static cl::opt<unsigned>
MaxArraySize("instcombine-maxarray-size", cl::init(1024),
cl::desc("Maximum array size considered when doing a combine"));
+// FIXME: Remove this flag when it is no longer necessary to convert
+// llvm.dbg.declare to avoid inaccurate debug info. Setting this to false
+// increases variable availability at the cost of accuracy. Variables that
+// cannot be promoted by mem2reg or SROA will be described as living in memory
+// for their entire lifetime. However, passes like DSE and instcombine can
+// delete stores to the alloca, leading to misleading and inaccurate debug
+// information. This flag can be removed when those passes are fixed.
+static cl::opt<unsigned> ShouldLowerDbgDeclare("instcombine-lower-dbg-declare",
+ cl::Hidden, cl::init(true));
+
Value *InstCombiner::EmitGEPOffset(User *GEP) {
return llvm::EmitGEPOffset(&Builder, DL, GEP);
}
@@ -2092,6 +2103,16 @@ Instruction *InstCombiner::visitAllocSit
// to null and free calls, delete the calls and replace the comparisons with
// true or false as appropriate.
SmallVector<WeakTrackingVH, 64> Users;
+
+ // If we are removing an alloca with a dbg.declare, insert dbg.value calls
+ // before each store.
+ DbgDeclareInst *DDI = nullptr;
+ std::unique_ptr<DIBuilder> DIB;
+ if (isa<AllocaInst>(MI)) {
+ DDI = FindAllocaDbgDeclare(&MI);
+ DIB.reset(new DIBuilder(*MI.getModule(), /*AllowUnresolved=*/false));
+ }
+
if (isAllocSiteRemovable(&MI, Users, &TLI)) {
for (unsigned i = 0, e = Users.size(); i != e; ++i) {
// Lowering all @llvm.objectsize calls first because they may
@@ -2124,6 +2145,8 @@ Instruction *InstCombiner::visitAllocSit
} else if (isa<BitCastInst>(I) || isa<GetElementPtrInst>(I) ||
isa<AddrSpaceCastInst>(I)) {
replaceInstUsesWith(*I, UndefValue::get(I->getType()));
+ } else if (DDI && isa<StoreInst>(I)) {
+ ConvertDebugDeclareToDebugValue(DDI, cast<StoreInst>(I), *DIB);
}
eraseInstFromFunction(*I);
}
@@ -2135,6 +2158,10 @@ Instruction *InstCombiner::visitAllocSit
InvokeInst::Create(F, II->getNormalDest(), II->getUnwindDest(),
None, "", II->getParent());
}
+
+ if (DDI)
+ eraseInstFromFunction(*DDI);
+
return eraseInstFromFunction(MI);
}
return nullptr;
@@ -3188,7 +3215,9 @@ static bool combineInstructionsOverFunct
// Lower dbg.declare intrinsics otherwise their value may be clobbered
// by instcombiner.
- bool MadeIRChange = LowerDbgDeclare(F);
+ bool MadeIRChange = false;
+ if (ShouldLowerDbgDeclare)
+ MadeIRChange = LowerDbgDeclare(F);
// Iterate while there is work to do.
int Iteration = 0;
Modified: llvm/trunk/test/Transforms/InstCombine/debuginfo-skip.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/debuginfo-skip.ll?rev=313108&r1=313107&r2=313108&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/debuginfo-skip.ll (original)
+++ llvm/trunk/test/Transforms/InstCombine/debuginfo-skip.ll Tue Sep 12 18:43:25 2017
@@ -1,12 +1,5 @@
-; RUN: opt < %s -instcombine -debug -S -o %t 2>&1 | FileCheck %s
-; RUN: cat %t | FileCheck %s --check-prefix=CHECK-IR
-; REQUIRES: asserts
-
-; Debug output from InstCombine should not have any @llvm.dbg.* instructions visited
-; CHECK-NOT: call void @llvm.dbg.
-
-; The resulting IR should still have them
-; CHECK-IR: call void @llvm.dbg.
+; RUN: opt -instcombine-lower-dbg-declare=0 < %s -instcombine -S | FileCheck %s
+; RUN: opt -instcombine-lower-dbg-declare=1 < %s -instcombine -S | FileCheck %s
define i32 @foo(i32 %j) #0 !dbg !7 {
entry:
@@ -18,6 +11,14 @@ entry:
ret i32 %0, !dbg !15
}
+; Instcombine can remove the alloca and forward the load to store, but it
+; should convert the declare to dbg value.
+; CHECK-LABEL: define i32 @foo(i32 %j)
+; CHECK-NOT: alloca
+; CHECK: call void @llvm.dbg.value(metadata i32 %j, {{.*}})
+; CHECK: call void @llvm.dbg.value(metadata i32 10, {{.*}})
+; CHECK: ret i32 %j
+
declare void @llvm.dbg.declare(metadata, metadata, metadata) #1
declare void @llvm.dbg.value(metadata, metadata, metadata) #1
Modified: llvm/trunk/test/Transforms/InstCombine/debuginfo.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/debuginfo.ll?rev=313108&r1=313107&r2=313108&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/debuginfo.ll (original)
+++ llvm/trunk/test/Transforms/InstCombine/debuginfo.ll Tue Sep 12 18:43:25 2017
@@ -1,48 +1,96 @@
-; RUN: opt < %s -instcombine -S | FileCheck %s
+; RUN: opt < %s -instcombine -instcombine-lower-dbg-declare=0 -S \
+; RUN: | FileCheck %s --check-prefix=CHECK --check-prefix=NOLOWER
+; RUN: opt < %s -instcombine -instcombine-lower-dbg-declare=1 -S | FileCheck %s
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64--linux"
+
+%struct.TwoRegs = type { i64, i64 }
declare void @llvm.dbg.declare(metadata, metadata, metadata) nounwind readnone
declare i64 @llvm.objectsize.i64.p0i8(i8*, i1) nounwind readnone
-declare i8* @foo(i8*, i32, i64, i64) nounwind
+declare i8* @passthru_callee(i8*, i32, i64, i64)
-define hidden i8* @foobar(i8* %__dest, i32 %__val, i64 %__len) nounwind inlinehint ssp !dbg !1 {
+define i8* @passthru(i8* %a, i32 %b, i64 %c) !dbg !1 {
entry:
- %__dest.addr = alloca i8*, align 8
- %__val.addr = alloca i32, align 4
- %__len.addr = alloca i64, align 8
- store i8* %__dest, i8** %__dest.addr, align 8
-; CHECK-NOT: call void @llvm.dbg.declare
-; CHECK: call void @llvm.dbg.value
- call void @llvm.dbg.declare(metadata i8** %__dest.addr, metadata !0, metadata !DIExpression()), !dbg !16
- store i32 %__val, i32* %__val.addr, align 4
- call void @llvm.dbg.declare(metadata i32* %__val.addr, metadata !7, metadata !DIExpression()), !dbg !18
- store i64 %__len, i64* %__len.addr, align 8
- call void @llvm.dbg.declare(metadata i64* %__len.addr, metadata !9, metadata !DIExpression()), !dbg !20
- %tmp = load i8*, i8** %__dest.addr, align 8, !dbg !21
- %tmp1 = load i32, i32* %__val.addr, align 4, !dbg !21
- %tmp2 = load i64, i64* %__len.addr, align 8, !dbg !21
- %tmp3 = load i8*, i8** %__dest.addr, align 8, !dbg !21
+ %a.addr = alloca i8*, align 8
+ %b.addr = alloca i32, align 4
+ %c.addr = alloca i64, align 8
+ store i8* %a, i8** %a.addr, align 8
+ call void @llvm.dbg.declare(metadata i8** %a.addr, metadata !0, metadata !DIExpression()), !dbg !16
+ store i32 %b, i32* %b.addr, align 4
+ call void @llvm.dbg.declare(metadata i32* %b.addr, metadata !7, metadata !DIExpression()), !dbg !18
+ store i64 %c, i64* %c.addr, align 8
+ call void @llvm.dbg.declare(metadata i64* %c.addr, metadata !9, metadata !DIExpression()), !dbg !20
+ %tmp = load i8*, i8** %a.addr, align 8, !dbg !21
+ %tmp1 = load i32, i32* %b.addr, align 4, !dbg !21
+ %tmp2 = load i64, i64* %c.addr, align 8, !dbg !21
+ %tmp3 = load i8*, i8** %a.addr, align 8, !dbg !21
%0 = call i64 @llvm.objectsize.i64.p0i8(i8* %tmp3, i1 false), !dbg !21
- %call = call i8* @foo(i8* %tmp, i32 %tmp1, i64 %tmp2, i64 %0), !dbg !21
+ %call = call i8* @passthru_callee(i8* %tmp, i32 %tmp1, i64 %tmp2, i64 %0), !dbg !21
ret i8* %call, !dbg !21
}
+; CHECK-LABEL: define i8* @passthru(i8* %a, i32 %b, i64 %c)
+; CHECK-NOT: alloca
+; CHECK-NOT: store
+; CHECK-NOT: call void @llvm.dbg.declare
+; CHECK: call void @llvm.dbg.value(metadata i8* %a, {{.*}})
+; CHECK-NOT: store
+; CHECK: call void @llvm.dbg.value(metadata i32 %b, {{.*}})
+; CHECK-NOT: store
+; CHECK: call void @llvm.dbg.value(metadata i64 %c, {{.*}})
+; CHECK-NOT: store
+; CHECK: call i8* @passthru_callee(i8* %a, i32 %b, i64 %c, i64 %{{.*}})
+
+declare void @tworegs_callee(i64, i64)
+
+; Lowering dbg.declare in instcombine doesn't handle this case very well.
+
+define void @tworegs(i64 %o.coerce0, i64 %o.coerce1) !dbg !31 {
+entry:
+ %o = alloca %struct.TwoRegs, align 8
+ %0 = bitcast %struct.TwoRegs* %o to { i64, i64 }*
+ %1 = getelementptr inbounds { i64, i64 }, { i64, i64 }* %0, i32 0, i32 0
+ store i64 %o.coerce0, i64* %1, align 8
+ %2 = getelementptr inbounds { i64, i64 }, { i64, i64 }* %0, i32 0, i32 1
+ store i64 %o.coerce1, i64* %2, align 8
+ call void @llvm.dbg.declare(metadata %struct.TwoRegs* %o, metadata !35, metadata !DIExpression()), !dbg !32
+ %3 = bitcast %struct.TwoRegs* %o to { i64, i64 }*, !dbg !33
+ %4 = getelementptr inbounds { i64, i64 }, { i64, i64 }* %3, i32 0, i32 0, !dbg !33
+ %5 = load i64, i64* %4, align 8, !dbg !33
+ %6 = getelementptr inbounds { i64, i64 }, { i64, i64 }* %3, i32 0, i32 1, !dbg !33
+ %7 = load i64, i64* %6, align 8, !dbg !33
+ call void @tworegs_callee(i64 %5, i64 %7), !dbg !33
+ ret void, !dbg !33
+}
+
+; NOLOWER-LABEL: define void @tworegs(i64 %o.coerce0, i64 %o.coerce1)
+; NOLOWER-NOT: alloca
+; NOLOWER-NOT: store
+; NOLOWER-NOT: call void @llvm.dbg.declare
+; NOLOWER: call void @llvm.dbg.value(metadata i64 %o.coerce0, {{.*}})
+; NOLOWER-NOT: store
+; NOLOWER: call void @llvm.dbg.value(metadata i64 %o.coerce1, {{.*}})
+; NOLOWER-NOT: store
+; NOLOWER: call void @tworegs_callee(i64 %o.coerce0, i64 %o.coerce1)
+
+
!llvm.dbg.cu = !{!3}
!llvm.module.flags = !{!30}
-!0 = !DILocalVariable(name: "__dest", line: 78, arg: 1, scope: !1, file: !2, type: !6)
-!1 = distinct !DISubprogram(name: "foobar", line: 79, isLocal: true, isDefinition: true, virtualIndex: 6, flags: DIFlagPrototyped, isOptimized: true, unit: !3, scopeLine: 79, file: !27, scope: !2, type: !4, variables: !25)
+!0 = !DILocalVariable(name: "a", line: 78, arg: 1, scope: !1, file: !2, type: !6)
+!1 = distinct !DISubprogram(name: "passthru", line: 79, isLocal: true, isDefinition: true, virtualIndex: 6, flags: DIFlagPrototyped, isOptimized: true, unit: !3, scopeLine: 79, file: !27, scope: !2, type: !4, variables: !25)
!2 = !DIFile(filename: "string.h", directory: "Game")
!3 = distinct !DICompileUnit(language: DW_LANG_C99, producer: "clang version 3.0 (trunk 127710)", isOptimized: true, emissionKind: FullDebug, file: !28, enums: !29, retainedTypes: !29)
!4 = !DISubroutineType(types: !5)
!5 = !{!6}
!6 = !DIDerivedType(tag: DW_TAG_pointer_type, size: 64, align: 64, scope: !3, baseType: null)
-!7 = !DILocalVariable(name: "__val", line: 78, arg: 2, scope: !1, file: !2, type: !8)
+!7 = !DILocalVariable(name: "b", line: 78, arg: 2, scope: !1, file: !2, type: !8)
!8 = !DIBasicType(tag: DW_TAG_base_type, name: "int", size: 32, align: 32, encoding: DW_ATE_signed)
-!9 = !DILocalVariable(name: "__len", line: 78, arg: 3, scope: !1, file: !2, type: !10)
-!10 = !DIDerivedType(tag: DW_TAG_typedef, name: "size_t", line: 80, file: !27, scope: !3, baseType: !11)
-!11 = !DIDerivedType(tag: DW_TAG_typedef, name: "__darwin_size_t", line: 90, file: !27, scope: !3, baseType: !12)
+!9 = !DILocalVariable(name: "c", line: 78, arg: 3, scope: !1, file: !2, type: !12)
!12 = !DIBasicType(tag: DW_TAG_base_type, name: "long unsigned int", size: 64, align: 64, encoding: DW_ATE_unsigned)
!16 = !DILocation(line: 78, column: 28, scope: !1)
!18 = !DILocation(line: 78, column: 40, scope: !1)
@@ -51,8 +99,19 @@ entry:
!22 = distinct !DILexicalBlock(line: 80, column: 3, file: !27, scope: !23)
!23 = distinct !DILexicalBlock(line: 79, column: 1, file: !27, scope: !1)
!25 = !{!0, !7, !9}
-!26 = !DIFile(filename: "bits.c", directory: "Game")
!27 = !DIFile(filename: "string.h", directory: "Game")
!28 = !DIFile(filename: "bits.c", directory: "Game")
!29 = !{}
!30 = !{i32 1, !"Debug Info Version", i32 3}
+
+!31 = distinct !DISubprogram(name: "tworegs", scope: !28, file: !28, line: 4, type: !4, isLocal: false, isDefinition: true, scopeLine: 4, flags: DIFlagPrototyped, isOptimized: true, unit: !3, variables: !34)
+!32 = !DILocation(line: 4, column: 23, scope: !31)
+!33 = !DILocation(line: 5, column: 3, scope: !31)
+!34 = !{!35}
+!35 = !DILocalVariable(name: "o", arg: 1, scope: !31, file: !28, line: 4, type: !36)
+!36 = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "TwoRegs", file: !28, line: 1, size: 128, elements: !37)
+!37 = !{!38, !39}
+!38 = !DIDerivedType(tag: DW_TAG_member, name: "x", scope: !36, file: !28, line: 1, baseType: !12, size: 64)
+!39 = !DIDerivedType(tag: DW_TAG_member, name: "y", scope: !36, file: !28, line: 1, baseType: !12, size: 64)
+!40 = !DISubroutineType(types: !41)
+!41 = !{!36}
Modified: llvm/trunk/test/Transforms/Util/simplify-dbg-declare-load.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/Util/simplify-dbg-declare-load.ll?rev=313108&r1=313107&r2=313108&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/Util/simplify-dbg-declare-load.ll (original)
+++ llvm/trunk/test/Transforms/Util/simplify-dbg-declare-load.ll Tue Sep 12 18:43:25 2017
@@ -1,4 +1,5 @@
-; RUN: opt -instcombine -S < %s | FileCheck %s
+; RUN: opt -instcombine -instcombine-lower-dbg-declare=1 -S < %s | FileCheck %s
+; RUN: opt -instcombine -instcombine-lower-dbg-declare=0 -S < %s | FileCheck %s --check-prefix=DECLARE
target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-pc-linux-gnu"
@@ -26,6 +27,11 @@ idxend:
ret void
}
+; Keep the declare if we keep the alloca.
+; DECLARE-LABEL: define void @julia_fastshortest_6256()
+; DECLARE: %cp = alloca %foo, align 8
+; DECLARE: call void @llvm.dbg.declare(metadata %foo* %cp,
+
attributes #0 = { nounwind readnone }
attributes #1 = { sspreq }
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